Apparatus for preventing well fires



GAS

2 Sheets-Sheet 1 Jan. 4, 1966 J. w. MARX APPARATUS FOR FREVENTING WELLFIRES Filed NOV. 20, 1963 BYZdy Jan. 4, 1966 J. w. MARX 3,227,215

APPARATUS FOR PREVENTING WELL FIRES Filed Nov. 20. 1963 2 Sheets-Sheet 2SEPARATOR ERBURDEN INVENTOR. J W. M A R X A TTG/PNE YS United StatesPatent r, t 3,227,215 i. f APPARATUS FOR PREVENTING WELL 'FIRES .lohn W.Marx, Bartlesville, Okla., assigner to Phillips Petroleum Company, acorporation of Delaware Filed Nov. 20, 1963, Ser. No. 325,121 8 Claims."(Cl. 16o-63) This `is a continuation-impart lapplication ofapplications Serial No. 732,730, tiled May 2, 1958, and Serial No.`857,629, filed December 7, 1959, now US. Patent No. 3,135,324.Application Serial No. 732,730 isa continuation-in-part of applicationSerial No. 526,388, liled August 4, 1955, and now abandoned.

This invention relates to apparatus for preventing borehole iires duringin situ combustion of a carbonaceous stratum to recover oil therefrom; aj a In situ combustion in `the Vrecovery of hydrocarbons fromunderground strata containing carbonaceous material is becoming moreprevalent in the petroleum industry. In this technique of production,combustion is initiated in the carbonaceous stratum and the resulting combustion zone is caused to move thru the stratum by either inverse ordirect air drive, `whereby the heat of combustion of alsubstantialproportion of the hydrocarbon in the stratum drives out and usuallyupgrades a substantial proportion of the unburned hydrocarbon material.

The ignition of carbonaceous material in a stratum around a boreholetherein followed by injection yof air thru the ignition borehole andrecovery of product hydrocarbons andcombustion gas thru another boreholein the stratum is a direct 'air -drive process for effecting `in situcombustion and recovery of hydrocarbons from the stratum. In this typeof operation the stratum frequently plugs in front of the combustionZone because a heavy' viscous liquid bank of hydrocarbon collects in thestratum in advance of the combustion zone which prevents movef ment ofair to the combustion process. To overcome this diiculty and to permitthe continued progress of the combustion zone thru the stratum, inverseair injection has been resorted to. By this technique, a combustion Zoneis established around an ignition borehole by any suitable means and airis fed thru the stratum -to the combustion zone from one or moresurrounding boreholes. j

In the process of recovering oil by underground cornbustion, it isgenerally necessary to inject air into the porous, permeable,oil-bearing rock for extended periods. Field test results to dateindicate that spontaneous ignition may 4occur during such air injectionat high pressures. For example, a petroleum company recently conductedan underground combustion field test in the South Belridge iield, KernCounty, California, in which premature spontaneous ignition occurred atthe central injection well in a ldirect injection system. Subsequentperformance indicated that this ignition was limited to the upperportion of the pay Zone, and that this partial ignition detracted fromthe r'ield performance Vin that it reduced the volumetric sweep eiciencyof the direct drive' front.

Spontaneous ignition at air injection wells in any counteriiowcombustion process would have even worse effects as it would forceimmediate shutdown and possibly result in loss of a whole well patternsince there would be burning at the Wrong places in the pattern.

Infield tests in which hydrocarbons Were recovered by in situlcombustion in a tar sand by inverse air injection it was found that amaterial proportion of theV injected air lay-passed the combustion frontand appeared in the production borehole along with producedhydrocarbons. Even in the ignited zones, air is believed to by-pass therire front because of thermal fracturing which provides some channelingtherethru. The by-passed oxygen mixes with the combustible products fomthe burning zones a 3,227,215y -letales tgl??? and appears in theproduction Well which isr generally above the ignition temperature ofthe hydrocarbonoxygen mixture when this happens, and field tests to dateindicate, as a rule rather than'the exception, that the mixture burns inthe production borehole and production tubing u nless suitableprecautions are taken. Temperatures in excess of 2500 F. have beenfrequently observed in a produc# tion borehole from this cause. Thistemperature has been `more than sufficient to melt downhole equipment onseveral occasions. Furthermore, if the by-passed oxygen quantity islarger, it may consume the entire product, thereby rendering' theprocess entirely useless. In addition, serious personnel hazards arecreated.

This invention is concerned with apparatus'aforpreventing undesirable orpremature' spontaneous combustion in either a direct or inverse drive insitu combustion process during injection of combustion-supporting,oxygen-containing gas thru an injection Well in the stratum beingproduced. It is also concerned with apparatus for preventing lire in aproduction Well in either a direct or a reverse drive process.

Accordingly, it is an object of the invention to provide apparatus forpreventing fire in a well associated with an in situ combustion process.Another object is to provide a means for maintaining the temperature ofa stratum adjacent an injection borehole, during air injection, belowignition temperature at ambient conditions. It is also an object of theinvention to provide apparatus for controllingand regulating boreholetemperatures. A further object is to provide apparatus for preventingcombustion of produced gases in a production well during either director inverse in situ combustion. Other objects of the invention willbecome apparent upon consideration of the accompanying disclosure. Y

A broad aspect of the invention comprises apparatus for sensing thetemperature either in an injection borehole within the stratum to be,produced .while injecting airor other combustion-supporting gas or inaproduction well during movement of a combustion front toward same, and,as the temperature approaches the ignition temperature of hydrocarbonmaterial in the borehole or in the wall of the borehole, injecting intothe borehole a line `dispersion of water, such as a water aerosol, insuflicient quantity or at a suicient rate to maintain the temperature ata safe margin below the ignition tern'perature. The apparatus comprises,inhcombinatiou with a cased well extending into the stratum being or tobe produced, a temperature sensing device' in the well within thestratum, a supply of Water under sufficient pressure for" injection anddispersion, a line leading from the water :supply into the well, a valvein this line, and means responsive to the sensed temperature of saidsensing device inoperative control of said valve.

A more `complete understanding of the invention may be hadtbyl referencetothe accompanying schematic drawing of which FIGURE 1 is an elevationthru a section of stratum showing an arrangement of apparatus inaccordance with thev invention; FIGURE 2 is an elevation in partialsection showing another embodiment of the' water dispersion means;FIGURE 3 is a view similar to FIGURE 2, showing another embodiment ofthe` water injection means; and FIGURE 4 is a similar elevation showinganother arrangement of apparatus in accordance with the invention.

Referring tov FIGURE 1, a carbonaceous stratnr'n 10, Stich as an oilsand, is penetrated by a well or borehole 12 provided with a casing 14extending to the stratum, and al wellhead 16. In one embodiment atherrnocouple 18 is suspended on a cablef 20, including an electricalcon! ductor cable 22, thru tubing- 24. Tubing 24 is provided with valvemeans (not shown) for maintaining au air tight seal around the cable.Movement of the cable up and down in the well is facilitated by pulleys26 and 28 or by other suitable means.

An air line 30 connects with casing 14 below the wellhead as shown orthis line may pass thru the wellhead, similarly to tubing 24. A blower32, or other suitable means, passes a stream of pressurized air thruline 30 into the well. A source of water under pressure, such as a tank34, is connected with the well either directly or thru line 30 by meansof line 36 containing motor valve 38. Water is admitted to tank 34 fromline 40 as needed and pressurizing gas is passed into tank 34 thru line42.

A temperature controller 44 is connected with cable 22 and with motorvalve 38. This instrument (44) is set to maintain a suitable welltemperature as sensed by thermocouple 18, such as not exceeding 300 or400 F., depending upon the spontaneous ignition temperature of theadjacent stratum.

It is also feasible to utilize a series of vertically spaced spacedapart themocouples such as 18, 46, and 48 in xed or verticallyadjustable position within stratum 10. In this arrangement, the maximumtemperature sensed by the Series of thermocouples actuates temperaturecontroller 44 which operates valve 38 to introduce dispersion of waterinto the injected gas.

The apparatus of FIGURE 1 is used to prevent spontaneous combustion inwell 12, particularly, in the adjacent stratum, during pressuring of thestratum prior to establishing in situ combustion in the stratum orduring use of this well to inject air to a combustion front movingtoward said well.

In FIGURE 2, a high-pressure water line 50 containing flow control valve52 leads into air line 30 and is positioned so as to direct water onto ahemispherical solid surface 54 on device 56. This arrangement ofapparatus assures the formation of a very nely divided water mist whichis carried by the injected air into the well.

In FIGURE 3, a steam line 58 leads thru casing 14 into the path of theinjected air and is provided with a ow control valve 60. This embodimentof the apparatus and process bleeds steam into the injection air toprovide water droplets needed to maintain control of the temperature ofthe stratum in the well.

It is sometimes necessary to utilize an air injection pressure ofseveral hundred to 1000 p.s.i.g. or more and it is, of course, essentialto have available water pressure well above the air injection pressure.In such cases the steam pressure in line 58 and the water pressure inlines 50 and 36 must be adequate to effect injection and dispersion ofthe water against the pressure within the air line or well.

The water aerosol or mist is injected continuously in small quantitiesor intermittently in larger quantities automatically or by handoperation of valve 38 or the corresponding valves in the otherembodiments of the apparatus. The quantity of water to be introducedvaries from about an ounce to or more pounds 1,000 standard cubic feetof gas, depending on the ainity of the reservoir hydrocarbon for oxygen,the injection pressure, and the nature of the emergency involved. Nativepetroleum and bitumens vary greatly in their oxygen affinity, i.e.,their tendency to ignite spontaneously. Heavy crude from Kern County,California, exhibits an oxygen demand of the order of 1,000 times asmuch as some typical Missouri bitumens. Such crude definitely tends toignite spontaneously upon prolonged exposure to high pressure air and,as previously pointed out, spontaneous ignition actually did occurduring preliminary air injection operations on a recent undergroundcombustion field test in the South Belridge field. While some crudes andbitumens exhibit far less tendency to ignite spontaneously than the KernCounty example, it is good insurance to have available in allunderground combustion operations means for injecting finely dispersedwater into the injection gas.

It might be well to note that the combustion front can itself toleratesmall quantities of well-dispersed water, so that injection well borescan thus be kept cool without extinguishing the countertiow combustionfront. The preferred and most advantageous cooling fluid is H2O inliquid form and/or steam form, but other coolants inert in the well boreambient and readily separable from the production eiiluent may beutilized. Such coolants include N2, CO2, combustion gases, etc. Theensuing decription of the invention will be limited to H2O as thecoolant but it is to be understood that other coolants may be utilized,even tho less advantageously.

Referring to FIGURE 4, a borehole 70, spaced from well 12 of FIGURE 1,penetrates carbonaceous stratum 10 and is provided with a casing 72,extending from ground level to the upper level of the stratum, and withproduction tubing 74, extending from adjacent the lower end of thecasing through well head 76'to separating means 78. Line 80 carrieswater from separator 78 to waste or to recycle to the process asdesired. Line 82 carries recovered hydrocarbons to refining or storagefacilities.

A water line 84 extends to a level in casing 72 adjacent the lower endof tubing 74, or to a lower level within stratum 10, and is providedwith a spray head or nozzle 85. Water line 84 passes through well head76 and connects with a supply source, such as water tank 88. A pump isinserted in line 84 for providing the desired pressure at spray head 86.Motor valve 92 is positioned in line 84 downstream of pump 90.ThermocoupleI 94, positioned in the well adjacent or below the lower endof production tubing 74 and preferably just above the level of spraynozzle 86, is connected with a temperaturerecorder-controller 96 whichis in operative control of motor valve 92.

Instruments 44 and 96 are conventional temperaturerecorder-controllerdevices which are available from sev eral sources. The Brown InstrumentCompany, of Philadelphia, Pa., is a supplier of this type of instrumentwhich is illustrated in their Bulletin No. 15-4, copyrightcd in 1942.Similar temperature-recorder-controllers are illustrated in Principlesand Methods of Telemetering, by Borden et al., Reinhold lPublishingCorporation, 330 W. 42nd St., New York 18, New York, copyrighted 1948.Chapter 13 of this publication at page 184 illustrates one type ofinstrument suitable for the instant application.

At the stage of the process illustrated in the drawing, the re front 98has advanced from borehole 70 through the stratum a substantial distancetoward surrounding air injection boreholes such as borehole 12 of FIGUREl. The product hydrocarbons pass through the burned out areaintermediate lire front 98 and borehole 70 to the borehole and intoproduction tubing 74 in conventional manner. Fire front 98 eventuallyprogresses to the injection boreholes and upon arrival, with continuedair injection, the front is reversed in direction and is driven back toborehole 70 by direct air drive, feeding upon the carbonized residueleft in the stratum during the inverse air injection phase of theprocess.

During the inverse air injection -phase of the process, the hydrocarbonsproduced in and around re front 98 by the heat of the combustion processand the flushing action of the combustion gases, principally in vaporform, pass into the borehole 70 at elevated temperatures around 1000 F.and sometimes as high as 1500 or 1600 F. In this type of in situcombustion, the produced hydrocarbons passing through the hot burned outzone back of the combustion front, together with O2 which by-passes thetire front, appear in admixture in the production borehole and thetemperature of the mixture sustains combustion, so that all of theoxygen present in borehole 70 consumes hydrocarbons and to that extentdestroys valu-- able products, as well as contributing to excessivetern,- peratures and damage to downhole equipment.

5. During the direct drivey of the combustion front from the injectionwells back to the production well, the far-ont travels through the stillhot burned out stratum and bypassed oxygen is again present `inproduction 'i0 in admixture with hot hydrocarbons thereby causingVborehole fires. The present invention prevents borehole 'fires or, if a.borehole tire develops, the process can be utilized to extinguish thesame and prevent the .occurrence .of further borehole combustiori. n

In operation of the invention, Water is sprayed `in to the borehole,preferably, under substantial pressure Such as to 90 p.s.i.g., through adownhole spray, such las 4spray 86, so as to maintain the Atemperature"in the. borehole in the stratum below combustion .supportingtemperature at the concentration of oxygen in the borehole. It has beenfound that borehole fires do not occur when the temperature of theborehole is maintained below about 750 F. and it is Apreferable tocontrolqthe injection of i water into the borehole so as to maintain thetemperature in the range of about 600 to about 700 F., althoughtemperatures as low ,as 500 and as high as 750 F. have been usedsuccessfully. At higher temperatures, particularly at higherconcentrations of oxygen, fire develops in the borehole and destroysvaluable hydrocarbons being produced. As the temperature in the boreholedrops below about 500 F., liquid products accumulate in the bottom ofthe borehole 4and water injected into the borehole forms an emulsiontherewith which greatly complicates the separation problem in separator78. In addition, at lower borehole temperatures the water-hydrocar bonemulsion in the bottom of the borehole is agitated by the ow of gasesintothe borehole and considerable erosion of the borehole wall belowcasing '72 occurs, with substantial amounts of sand and eroded materialfrom the borehole appearing `in the production effluent, furthercomplicating the separation process. In other 4respects, at temperaturesbelow 500 F., the process is just as effective in preventing boreholefires and preserving valuable hydrocarbons, but operation in this mannerintroduces other problems and disadvantages to the process which areundesirable.

While it is preferred to inject water in the manner shown in the drawingit has also been found effectiveV `to merely spray or otherwise injectwater into the `mouth of the borehole at ground level, whereby the waterdescends by gravity into the :hot downhole section of the borehole whereit effectively cools the p-roduction effluent so as to prevent thecombustion of hydrocarbons with bypassed oxygen and thereby avoids wellbore res.'

A preferred method of operation comprisessensmg the temperature adjacentthe upper level of the stratum being produced by means of therniocouple94, or other tem-l temperature in the Well bore adjacent the producing.

stratum has been found satisfactory in a number of well tests. It is notnecessary that the injection of Water be continuous, as intermittentinjection of water has been successfully tested.

Field tests in inverse air injection insitu combustion in a tar sand ofsubstantialV thickness at a level between 50 and 80 feet below thesurface extending over aperiod of several months have been completedutilizing injection of water into the production boreholes at variouslevels in the well bore both intermittently and continuously. Theinjection of water in the manner described was found to becompletelyetfective in eliminating borehole lires when the thetemperature was maintained below the range of 700 to 750 F. It wasfoundthat when as low a `concentration ,of-oxygen in the productionwelll bore as 0.5 volume percent occurred, the temperature in the Wellbore rose from about 1000 F. to the yrange of 1500 to 1600 F., withoutinjection of water into the borehole, and with an oxygen concentrationof only 3.0 percent, the temperature rose to at least 2500 F. Oilproduction without borehole combustion was sustained in some of thesetests in which as much as percent of the injected air by-passed the tirefront and where the non-condensible efuent gas contained more than 18percent oxygen. It was surprising that the critical maximum boreholetemperature was as high as the range of 700 to 750 and that operation atborehole temperatures below about 500 F. was so undesirable because of.complicating problems resulting therefrom.

A preferred method of initiating in situ combustion in and around theignition `or production borehole in an inverse burning process`comprises heating the wall of the borehole within the carbonaceousstratum to ignition temperature and, while at this temperature, passingair thru the stratum into the borehole from one or more sur.- roundinginjection boreholes so as to initiate combustion of the carbonaceousmaterial in the stratum. Thereafter, continued passage of air thru `thestratum to the ignition borehole causes the resulting combustion zone orfront to move thru the stratum countercurrently to `the injected air. Itis advantageous to incorporate a small percent fuel gas, such as :1 ,tov,2% propane, with the injected air while initiating in situ combustion.

While the simplest method of injecting water into the hot productionborehole within the stratum is thru a water line leading into theborehole and, preferably, to a level just above the stratum, it is alsoyfeasible to inject water into the borehole, or its wall, from one ormore ,boreholes in the stratum within a short radius, such as one toseveral feet from the production borehole. Water injected in this mannerinto the wall of the production borehole has the beneficial cooling anddiluting effect but requires drilling extra boreholes and is lessdesirable for this reason.

While the foregoing description of the invention is limited to fluidcoolants, it is feasible to use readily Vaporizable solid coolants suchas particulate, solid CO2 (Dry Ice) or ordinary ice, although theproblem of introducing these materials to the well bore is a factor tobe considered which makes injection of liquid H2O or gaseous CO2preferable.

It has been found in inverse air injection field tests that the rate ofair injection must be at least about 20 standard cubic feet per squarefoot of combustionl front per hour in order to sustain a combustionfront moving inversely to the air flow. When the air injection rate isreduced below this minimum, the combustion front is either reversed indirection, so as to turn back to the production borehole, or the tiregoes out. The upper limit of the air injection rate depends uponeconomic factors such as compressor loss consumption of valuablehydrocarbons in the stratum and the character of the carbonaceousstratum itself; however, air rates of about 50 standard cubic feet persquare foot of lire front per hour are marginal and can be economicallyutilized, while air rates of s.c.f.h. per square foot of fire front aregenerally uneconomical and are maximum in any type of stratum.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I claim:

1. Apparatus for controlling temperature in a cased injection well usedin an in situ combustion process which comprises in combination:

(1) at least one temperature sensing device in said Well adjacent a payzone therein; ('2) a conduit leading thru the casing of said well for(7) means actuatably connected to said temperature sensing device andresponsive thereto for opening said motor valve when the temperatureadjacent said temperature sensing device reaches a predetermined value;and 'i (8) means for raising and lowering said temperature sensingdevice within said well during gas injection. 2. The apparatus of claim1 wherein a plurality of temperature sensing devices are positioned invertically spaced-apart arrangement within the portion of well withinsaid pay zone for sensing temperatures at different levels therein, saidtemperature controller being actuated by the maximum temperature sensedby said devices.

3. Apparatus for preventing well re in a well in use in an in situcombustion process which comprises in com-v bination:

(l) temperature sensing means in said well adjacent an oil-bearingstratum for sensing temperature' therein; (2) means for lowering andraising the means of (1) in said well;

(3) a tubing extending thru the well head into said (4) an injectionline for coolant communicating with said well;

(5) ow control means in the line of (4); and v l(i6) means responsive tothe temperature sensing means of (l) in operative control of the flowcontrol means of (5) for opening said ow control means when thetemperature adjacent said sensing means reaches a predetermined valueand controlling flow of coolant to substantially maintain a settemperature in said well adjacent the sensing meansof 1).

4. The apparatus of claim 3 wherein the injection line of (4) extends tothe level of said stratum and including a spray head on the lower endthereof.

S. The apparatus of claim 3 wherein said well is a production well in areverse drive in situ combustion operation, the tubing of (3) is aproduction tubing, and the injection line of (4) is a Water line.

6. Apparatus for controlling the temperature in a well penetrating astratum undergoing in situ combustion comprisingin combination:

(1) temperature sensing means in said well for sensing temperaturetherein; A

(2) means for lowering and raising the means of (l) in said well;

( 3) an air injection line communicating with said Well for injectingair therein;

(4) an injection line for water communicating with the line of "(3,

(5) flow control means in the line of (4); and

(6) means responsive to the temperature sensing means of (1) inoperative control of the flow control means of (5) fori? opening said owcontrol means when the temperature adjacent said sensing means reaches apredetermined value and controlling flow of coolant to substantiallymaintain a set temperature in said well adjacentthe sensing means of(l).

7. The apparatus of claim 6 including water dispersing means in the lineof (3) adjacent the delivery end of the line of (4). f,

S. Apparatus for controlling the temperature in a well penetrating astratum undergoing in situ combustion comprising in combination:

(l) a plurality of temperature sensing devices positioned in verticallyspaced-apart arrangement within the portion of Well within said stratumfor sensing vtemperatures at dierent levels therein;

(2) a conduit leading into said well for conduction of gases;

(3) a supply of coolant under pressure;

(4) a coolant line leading from the supply of (3) into said wellfor.,injecting coolant thereto;

(5). a motor valve in the line of (4); and

(6) means actuatably connected to the temperature sensingY devices of(1) and responsive to the maximum temperature sensed by said devices foropening the motor valve of (5) when the maximum temperature adjacentsaid stratum sensed by said devices reaches a predetermined value.

References Cited by the Examiner UNITED STATES PATENTS 724,053 3/1903Schroeder 239-4432 X 1,539,667' 5/1925 Halagarda 137-79 2,041,3945-/1936 Belcher 166-90 2,630,307 3/1953 Martin 166-4 2,853,136 9/1958Moore et al. 166-11 2,858,891 y11/1958 Mollet al 166-11 2,930,598 3/1960`Parker 166-11 X 3,013,609 12/19'61 Ten Brink 166--39 CHARLES E.ocoN-NELL, Primary Examiner. i BENJAMINHERSH, Examiner.

3. APPARATUS FOR PREVENTING WELL FIRE IN A WELL IN USE IN AN IN SITUCOMBUSTION PROCESS WHICH COMPRISES IN COMBINATION: (1) TEMPERATURESENSING MEANS IN SAID WELL ADJACENT AN OIL-BEARING STRATUM FOR SENSINGTEMPERATURE THEREIN; (2) MEANS FOR LOWERING AND RAISING THE MEANS OF (1)IN SAID WELL; (3) A TUBING EXTENDING THRU THE WELL HEAD INTO SAID WELL;(4) AN INJECTION LINE FOR COOLANT COMMUNICATING WITH SAID WELL; (5) FLOWCONTROL MEANS IN THE LINE OF (4); AND (6) MEANS RESPONSIVE TO THETEMPERATURE SENSING MEANS OF (1) IN OPERATIVE CONTROL OF THE FLOWCONTROL MEANS OF (5) FOR OPENING SAID FLOW CONTROL MEANS WHEN THETEMPERATURE ADJACENT SAID SENSING MEANS REACHES A PREDETERMINED VALUEAND CONTROLLING FLOW OF COOLANT TO SUBSTANTIALLY MAINTAIN A SETTEMPERATURE IN SAID WELL ADJACENT THE SENSING MEANS OF (1)